This invention relates broadly to a power transfer arrangement for providing power to the electrical system of a building and, more particularly, pertains to a power transfer arrangement provided with a monitor indicating the health or condition of the generator during utility power interruption.
Portable generators may be used in certain situations to feed electrical power to residential and commercial load circuits during a utility power outage. These systems in their most basic form include a generator or other auxiliary source of power positioned exteriorly of a building. The generator is connected to a power inlet box and a transfer switching mechanism which continues the electrical path through integral overcurrent protectors associated with the transfer switching mechanism to supply power to certain selected circuits of the load center as determined by the transfer switching mechanism circuit breakers. The circuits of the transfer switching mechanism are wired to selected circuits of the load center through wiring housed within a conduit extending between the load center and the transfer switching mechanism.
The present invention relates to a power transfer switching mechanism for interposition between an auxiliary power source and electrical load center of a building. Such a switching mechanism typically includes a cabinet having a front panel which may be provided with a set of switches and overcurrent protectors, each of which corresponds to a particular load circuit. A direct electrical connection is established between the power inlet box and the transfer switching mechanism as set forth in assignee""s U.S. Pat. No. 6,107,701 issued Aug. 22, 2000. The overcurrent protectors are mounted to a bus bar in the cabinet for receiving power from the generator to provide auxiliary power to selected circuits of the load center. The set of switches associated with the overcurrent protectors is mounted to the panel for controlling the supply of generator power from the switching mechanism to the building load center. Power indicating structure in the form of a pair of watt meters is typically included in the panel for representing the amount of power provided by the generator. Traditionally, one watt meter is associated with one group of load circuits and the other watt meter is associated with the remaining group of load circuits. Typically, one visually monitors the watt meters to see that the generator power to the loads remains balanced. Each watt meter has a transparent window having a support member for mounting a black-on-white wattage scale visible through the window, and an indicator mounted for movement along the scale in response to the supply of generator power.
It is important to understand that the so-called watt meters do not measure and display real time wattage being supplied by the generator. Instead, these watt meters are actually ammeters which measure and display the current or amperage being carried by the generator. The current is represented as wattage on the scale by multiplying it by an average constant voltage of 125 volts so that only an approximation of generator power is available on the front panel of the switching mechanism. In addition, the prior art power indicating structure also does not measure and display the real time generator output voltage which is not constant and can vary from 104 to 140 volts. Monitoring the real time voltage can be useful in detecting an over voltage condition which indicates a more serious problem in the voltage regulator or miswiring of the system. In addition, the prior art watt meters have a construction which makes visual monitoring of the generator status difficult at distances spaced from the front panel of the switching mechanism. It is also noted that the prior art power indicating structure does not include any type of indicator for confirming when utility power is restored so that the operator can correct the configuration of switches on the switching mechanism.
Accordingly, it would be desirable to provide the power transfer switching mechanism with an enhanced power indicating structure embodied in a generator status information display which accurately measures and more vibrantly displays real time wattage and voltage supply by the generator during a utility power interruption. It would also be desirable to provide the power transfer switching mechanism with an indicator which signifies whether or not utility power is driving the loads.
It is one object of the present invention to provide a generator condition monitor for quickly ascertaining the health or status of an electrical power system having capability of using utility or generator power.
It is also an object of the present invention to provide a generator status information display which employs tri-color, light emitting diodes (LEDs) to show actual wattage and voltage levels when generator power is operational in the electrical power system.
It is an additional object of the present invention to provide a display field on the front panel of a power transfer switching mechanism with a climbing bar graph wherein both the height of the graph and the color of the graph are indicative of the real time power consumption status of the generator.
It is a further object of the present invention to provide a display field on the front panel of a power transfer switching mechanism with a moving dot graph wherein both the relative position of the dot and the color of the dot are indicative of the real time output voltage of the generator.
It is yet another object of the present invention to provide a display field on the front panel of the power transfer switching mechanism with an indicator showing whether or not utility power is available through the electrical power system.
In one aspect of the invention, a power transfer arrangement is provided for supplying power from a generator to the electrical system of a building in the event of a utility power interruption. The power transfer arrangement has a power transfer switching mechanism adapted for interconnection with the building electrical system and includes a cabinet having panel structure provided with various electrical components for transferring power to various load circuits. The switching mechanism is improved by a generator status information display mounted on the cabinet for separately measuring and simultaneously displaying actual wattage and voltage supply by the generator to the load circuits. The generator status information display includes at least a three color LED scheme for indicating acceptable, cautionary and overage conditions. The generator status information display is comprised of a pair of electronic wattage graphs, each wattage graph being flanked by an electronic voltage graph. The generator status information display also includes an indicator representing the availability of utility power.
In another aspect of the invention, a generator condition monitor is provided for a power transfer switching mechanism adapted for interconnection with a building electrical system during a utility power interruption. The monitor includes at least one climbing bar graph where both the size and color of the graph are indicative of real time power consumption of the generator. The monitor also includes at least one moving dot graph wherein the relative position and color of the dot are indicative of the real time output voltage of the generator. The climbing bar graph and the moving dot graph both employ red, green and yellow LEDs to represent various condition levels of the generator. The climbing bar graph includes twenty LED segments and the moving dot graph includes ten LED segments. The monitor includes a single LED indicator representing the availability of utility power. The moving dot graph employs yellow LEDs to signify output voltages below 108 volts and above 132 volts and red LEDs to signify output voltages below 104 volts and above 136 volts. The climbing bar graph employs yellow LEDs to signify power consumption between 90 and 100 percent of capacity and red LEDs to signify power consumption above 100 percent of capacity.
Various other objects, features and advantages of the invention will be made apparent from the following description taken together with the drawings.